The excavation and maintenance of buried natural gas pipelines can lead to deformation and stress redistribution of the pipelines and even cause secondary damage to the pipes with issues. To clarify the impact of excavation unloading on buried pipelines, this study established a finite element three-dimensional pipe-soil model, investigated the mechanical response of pipelines under layered excavation and evaluated various parameters impacting the response. The parameters analyzed include the diameter-thickness ratio of the pipe, excavation length and width, thickness of top covering soil, elastic modulus of soil, specific weight of soil and initial displacement of the pipeline. The study results showed that the pipeline bulges upwards during excavation unloading, the pipe top in the middle is under tension, and the bottom of the pipe is under compression. Therefore, the axial stress and vertical displacement both increase first and then decrease, and they are distributed symmetrically along the pipeline axis; excavating the initially compressed pipeline leads to high strain areas in the pipeline and even local buckling. The response to slope excavation is more pronounced than that to straight trench excavation; the additional response of the pipeline increases with the increase of diameter-thickness ratio, excavation width, thickness of pipe top covering soil and specific weight of soil, but it decreases with the increasing soil elastic modulus. The additional response is closely related to excavation length and the initial displacement. The results of this study can provide a reference for pipeline construction, maintenance, and safety assessment.

埋地天然气管道的开挖和维护会导致管道变形和应力重新分布，甚至造成管道的二次损坏。为了明确开挖卸荷对埋地管道的影响，建立了有限元三维管土模型，研究了分层开挖下管道的力学响应，评估了影响响应的各种参数。分析的参数包括管道的径厚比、开挖长度和宽度、顶覆土的厚度、土的弹性模量、土的比重和管道的初始位移。研究结果表明，开挖卸荷时管道向上凸出，中部管顶受拉，管底受压。因此，轴向应力和竖向位移均先增大后减小，且沿管道轴线对称分布；挖掘最初压缩的管道会导致管道中产生高应变区域，甚至局部屈曲。边坡开挖的响应比直沟开挖的响应更明显；管道附加响应随着径厚比、开挖宽度、管顶覆盖土厚度和土比重的增大而增大，但随着土弹性模量的增大而减小。附加响应与开挖长度和初始位移密切相关。研究结果可为管道建设、维护和安全评估提供参考。